Pigment dispersants for coating compositions

ABSTRACT

Pigment dispersants for use in coating compositions wherein the dispersant is the polymerization product of (i) an alkyl methacrylate having from 3 to 8 carbon atoms in the alkyl group, (ii) a hardening monomer selected from the group consisting of a styrene, methyl methacrylate, ethyl methacrylate and mixtures thereof, (iii) an ethylenically unsaturated carboxylic acid selected from the group consisting of acrylic acid, methacrylic acids, itaconic acid, crotonic acid, maleic acid, fumaric acid and mixtures thereof or a monomer having a double bond alpha-beta to a carbonyl group and which provides carboxyl functionality when reacted with water, alcohol, amine or anhydride, (iv) a monomer having a double bond alpha-beta to a carbonyl group and at least one hydroxyl group or a monomer which provides such groups when further reacted with an acid or an epoxide, and (v) a compound providing an amine or amine salt functional moiety. The dispersants are useful for dispersing pigments in coating compositions containing a wide variety of film-forming resins.

This is a division of application Ser. No. 166,643, filed July 7, 1980which is a continuation of application Ser. No. 938,746, filed Aug. 31,1978, now abandoned.

BACKGROUND OF THE INVENTION

The subject invention relates to (1) pigment dispersants, (2) their usein pigment dispersions containing pigment and liquid carrier and (3)coating compositions containing the pigment dispersions. The dispersantsare useful in the manufacture of a wide variety of pigmentedresin-containing coating compositions.

Pigmented coating compositions are useful for their aesthetic as well asprotective features. Such compositions contain a film-forming resn and apigment dispersed in a liquid carrier. It is important that the pigmentbe satisfactorily dispersed throughout any film which results from theapplication of the coating composition. It is therefore desirable thatthe pigment be well dispersed throughout the liquid coating composition.Typically, the pigment to be used in a coating composition is firstdispersed with only a portion of the total film-forming resin of whichthe coating composition is comprised together with appropriate liquidcarriers and additives. The resulting dispersion is then mixed with theremainder of the film-forming resin and any other necessary componentsto produce the coating composition. Most pigment dispersants are veryspecific in their performance and are compatible with only a smallnumber of the diverse solvents and film-forming resins used in coatingcompositions. For example, in the case of an acrylic resin based coatingcomposition, the pigment will be first dispersed with a portion of theacrylic resin in the presence of an organic solvent. The resultantproduct is then further diluted with the remainder of the acrylic resinand any other necessary components forming a part of the coatingcomposition. The final color of the coating composition is normallyadjusted by small further additions of pigment dispersions containingthe same or similar film-forming resins just prior to use. This furtheraddition is normally referred to as "tinting".

A number of different film-forming resins are used in the manufacture ofdifferent coating compositions. Accordingly, heretofore it has beennecessary to predisperse pigments with a portion of the film-formingresin or a resin compatible therewith, which is appropriate to each typeof coating composition. That is, even though the pigmentation of twocoating compositions containing different film-forming resins may beidentical, it has been necessary to disperse each pigment or mixture ofpigments separately with the appropriate film-forming resin. This isnecessary so as to avoid any problems of incompatibility in the finalcoating composition. In a similar manner any tinting operation requiresthe use of dispersants which are compatible with the film-forming resinbeing used.

One solution to the aforementioned well-known problem has been thedevelopment of so called "multi-purpose" pigment grinding vehicles. Thepolymeric dispersants contained in the mult-purpose pigment grindingvehicles are compatible with a wide range of film-forming resins andsolvents. It can readily be recognized that a pigment grinding vehiclewhich can be used in many coating systems would be of significantsavings to the coatings industry. Thus, one set of pigment dispersionscould be used with a wide variety of coating compositions.

There have now been found dispersants based on the polymerizationproducts of specific monomeric units which are capable of acting asmulti-purpose dispersants. Such dispersants are useful for dispersingpigments and which can then be used in resin-containing coatingcompositions.

As used herein all percentages and ratios are by weight unless otherwiseindicated.

SUMMARY OF THE INVENTION

A dispersant compatible with a variety of film-forming resins is thepolymerization product of (i) from about 20 percent to about 85 percentof an alkyl methacrylate having from 3 to 8 carbon atoms in the alkylgroup, (ii) from about 5 percent to about 60 percent of a hardeningmonomer selected from the group consisting of a styrene, methylmethacrylate, ethyl methacrylate and mixtures thereof, (iii) from about1 percent to about 25 percent of an ethylenically unsaturated carboxylicacid selected from the group consisting of acrylic acid, methacrylicacid, itaconic acid, crotonic acid, maleic acid, fumaric acid andmixtures thereof or a monomer having a double bond alpha-beta to acarbonyl group and which provides carboxyl functionality when reactedwith water, alcohol, amine or anhydride, (iv) from about 1 percent toabout 25 percent of a monomer having a double bond alpha-beta to acarbonyl group and at least one hydroxyl group or a monomer whichprovides such groups when further reacted with an acid or epoxide, and(v) from about 0.1 percent to about 15 percent of a compound providingan amine or amine salt functional moiety; and wherein said dispersanthas a weight average molecular weight as determined by gel permeationchromatography, using a polystyrene standard of from about 1,000 toabout 10,000.

The above-described dispersants are especially adapted for dispersingpigments to be used in coating compositions wherein the film-formingresin is an epoxy, vinyl, alkyd, polyester, acrylic, aminoplast,phenolplast, cellulose derivative, amide, or urethane resin or mixturesthereof.

DETAILED DESCRIPTION OF THE INVENTION

The invention herein described relates to (1) dispersants, (2) pigmentdispersions containing the dispersant, pigment and liquid carrier and(3) coating compositions containing the dispersant, pigment,film-forming resin and a liquid carrier.

Dispersants

The dispersants described herein are the polymerization product of analkyl methacrylate, a hardening monomer, an ethylenically unsaturatedcarboxylic acid or a monomer having a double bond alpha-beta to acarbonyl group and which provides carboxyl functionality when reactedwith water, alcohol, amine or anhydride, a monomer having or providing acarbonyl group with a double bond alpha-beta to the carbonyl group andat least one hydroxyl group and a compound providing an amine or aminesalt functional moiety. Each of the individual components used informing the polymer is described in the succeeding paragraphs. Thepercentages of the individual components are given on the basis of thenon-volatile components.

The alkyl methacrylate is used in the formation of the polymer at alevel of from about 20 percent to about 85 percent, preferably fromabout 40 percent to about 80 percent, and more preferably from about 60percent to about 80 percent of the reaction mixture. The alkylmethacrylates contain from 3 to 8 carbon atoms in the alkyl chain.Examples of satisfactory alkyl methacrylates include isopropylmethacrylate, butyl methacrylate, isobutyl methacrylate, isoamylmethacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate and octylmethacrylate. The branched chain methacrylates are preferred withisobutyl methacrylate being the most preferred alkyl methacrylate.

A hardening monomer selected from the group consisting of a styrene,methyl methacrylate, ethyl methacrylate and mixtures thereof is used information of the herein described polymer at a level of from about 5percent to about 60 percent, preferably from about 15 percent to about40 percent, more preferably from about 20 percent to about 35 percent. Astyrene, as used herein, is intended to include styrene and thesubstituted styrenes, e.g., alpha-methyl styrene, vinyl toluene,chlorostyrene, and tert-butylstyrene. Styrene and methyl methacrylateare the preferred hardening monomers.

From about 1 percent to about 25 percent, preferably from about 1percent to about 20 percent, more preferably from about 1 percent toabout 15 percent, of the reaction mixture comprises the ethylenicallyunsaturated carboxylic acid or a monomer having a double bond alpha-betato a carbonyl group and which provides carboxyl functionality whenreacted with water, alcohol, amine or anhydride. The ethylenicallyunsaturated carboxylic acid is selected from the group consisting ofacrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleicacid, fumaric acid and mixtures thereof. Acrylic acid and methacrylicacid are the preferred ethylenically unsaturated carboxylic acids.

Instead of polymerizing the ethylenically unsaturated carboxylic acidinto the polymer, other monomers can be used which when further reactedprovide the carboxyl functionality. Thus, alkyl acrylates such as methylor ethyl acrylate can be polymerized into the polymer and thereafterhydrolyzed. Another technique of introducing the carboxyl functionalityto the polymer is to use an unsaturated anhydride, e.g., maleicanhydride or substituted maleic anhydride, in the initial polymerizationreaction followed by the opening of the anhydride with (1) water toyield a diacid, (2) an alcohol to yield an ester acid or (3) an amine toyield an amide acid. The alcohol and amine are alkyl, aryl orcycloaliphatic in nature and include methyl alcohol, ethyl alcohol,2-ethylhexyl alcohol, the phenols and napthols, cyclohexanol, furfurylalcohol, ethyl amine, hexyl amine, diethyl amine, dibutyl amine,aniline, alkyl substituted anilines, piperidine and morpholine. Stillanother method of providing the carboxyl functionality in the polymer isto use a hydroxyl- or amine-containing monomer in preparing the polymerand thereafter react it with an anhydride. The reaction of the hydroxylgroup with an anhydride gives an ester acid while the reaction of theamine group with an anhydride gives an amide acid. Monomers that providethe hydroxyl groups in the polymer include the hydroxyalkyl acrylatesand methacrylates, e.g., hydroxyethyl acrylate, hydroxypropyl acrylateand hydroxyethyl methacrylate. Monomers that provide the amine groupsinclude tert-butylaminoethyl methacrylate and aziridine reactionproducts which furnish amine functionality pendent from the polymer.

The polymer reaction mixture also contains from about 1 percent to about25 percent of a monomer having a double bond alpha-beta to a carbonylgroup and at least one hydroxyl group or a monomer which provides suchgroups when further reacted with an acid or an epoxide. The preferredlevel of this component ranges from about 1 percent to about 15 percent,with the more preferred level being from about one percent to about 10percent. Examples of monomers having a double bond alpha-beta to acarbonyl group and at least one hydroxyl group are the monohydroxy alkylacrylates, alkyl methacrylates and alkyl crotonates and the mono- anddihydroxy alkyl fumarates, itaconates, and maleates. Preferred are thehydroxyl-containing alkyl acrylates and methacrylates with the alkylgroup containing from 2 carbon atoms to 20 carbon atoms, preferably from2 carbon atoms to 6 carbon atoms. Suitable hydroxyl-containing monomersinclude hydroxyethyl acrylate, hydroxypropyl acrylates, hydroxyethylmethacrylate and hydroxypropyl methacrylate, with hydroxyethyl acrylatebeing preferred.

Examples of monomers which provide the carbonyl group with thealpha-beta unsaturation and at least one hydroxyl group when reactedwith an acid are the glycidyl acrylates and glycidyl methacrylates. Theglycidyl acrylate or methacrylate is reacted with the other describedmonomers to form a polymerization product, which is then reacted with anacid such as acetic acid, lauric acid, benzoic acid, or nicotinic acidto open the epoxide ring. It will be recognized that anitrogen-containing acid used to open the epoxide ring can also be usedto introduce the amine functional moiety (as below discussed) to thedispersant. The resultant polymerization product contains a carbonylgroup with alpha-beta unsaturation to a carbonyl group and at least onehydroxyl group.

Monomers which provide a carbonyl group with the alpha-beta unsaturationand at least one hydroxyl group when reacted with an epoxide are acrylicand methacrylic acid. Thus, a polymer which is formed as describedherein using acrylic or methacrylic acid as monomer (iv) is formed andthen reacted with an epoxide. Suitable epoxides include styrene oxide,glycidol, ethylene oxide, propylene oxide, 1,2- and 2,3-butylene oxide,butyl glycidyl ether, phenyl glycidyl ether and a glycidyl ester of asaturated C₉₋₁₁ tertiary monocarboxylic acid. The reaction of theacrylic or methacrylic units of the interpolymer with the epoxideresults in the formation on the polymer of a carbonyl group with thealpha-beta unsaturation and at least one hydroxyl group.

A fifth component used in the formation of the polymer is a compoundcapable of providing an amine or amine salt functional moiety. Thiscompound is used at a level ranging from about 0.1 percent to about 15percent, preferably from about 0.5 percent to about 3 percent of thepolymer reaction mixture. The amine salt functional moiety can beprovided by an aliphatic or alicyclic amine which forms a salt with thecarboxyl moiety of the interpolymer compound. Examples thereof includeoleylamine, cyclohexylamine, dimethylbenzylamine, dimethylethanolamine,diethylethanolamine and stearylamine. One source of amine functionalmoieties is provided by an acrylic or methacrylic compound containingamino groups, e.g., dimethylaminoethyl methacrylate, ethyl-, propyl- andt-butylaminoethyl acrylate and t-butylaminoethyl methacrylate or 2- and4-vinyl pyridine. Such compounds are polymerized into the backbone ofthe interpolymer. Additionally, the amine functional moiety can beprovided by the inclusion of a nitrogen-containing ring opening compoundin the polymerization reaction mixture. Such compounds are representedby the following formula: ##STR1## where R₁, R₂, R₄, R₅, and R₆ are eachhydrogen; alkyl having up to 20 carbon atoms, e.g., methyl, ethyl orpropyl; aryl, e.g., phenyl; alkaryl, e.g., tolyl or xylyl; or aralkyl,e.g., benzyl or phenethyl. R₃ is hydrogen or a lower alkyl having from 1to 6 carbon atoms and n is 0 or 1. Examples of suitable compounds usefulherein include: ethylenimine (aziridine), 1,2-propylenimine,1,3-propylenimine, 1,2-dodecylenimine, 1,1-dimethyl ethylenimine, phenylethylenimine, benzyl ethylenimine, tolyl ethylenimine, hydroxyethylethylenimine, aminoethyl ethylenimine, 2-methyl propylenimine, N-ethylethylenimine, N-phenyl ethylenimine and N-tolyl ethylenimine. Thepreferred aziridine compounds are the alkylenimines having 2 to 4 carbonatoms, especially ethylenimine and 1,2-propylenimine.

The polymers are made by conventional solution polymerization of theaforedescribed individual components in an inert organic solvent. A socalled "one shot" procedure can be used wherein each of the individualmonomers is present at the start of the polymerization reaction. Thereaction is conducted at a temperature of from about 80° C. to about160° C., preferably from about 120° C. to about 145° C. for from about45 minutes to about 6 hours, preferably about 90 minutes to about 21/2hours. Examples of suitable inert organic solvents include thefollowing: ether-type alcohols, e.g., ethylene glycol monobutyl ether,ethylene glycol monoethyl ether and propylene glycol monobutyl ether,ethanol, propanol, isopropanol and butanol. The polymerization iscarried out in the presence of a vinyl polymerization catalyst.Preferred catalysts are the azo compounds, e.g., alpha,alpha'-azobis(isobutyronitrile), tertiary butyl perbenzoate, tertiarybutyl pivalate, isopropyl percarbonate and benzoyl peroxide. It shouldbe recognized that the resultant reaction product can be isolated orhave a part of the solvent removed. Preferably, however, the solvent isretained for convenience in later forming the pigment dispersion and thecoating composition containing same.

The resultant polymers have a weight average molecular weight determinedby gel permeation chromatography, using a polystyrene standard, of fromabout 1,000 to about 10,000, preferably from about 2,000 to about 6,000.A molecular weight below about 1,000 is to be avoided inasmuch as theresultant polymer is too brittle and will not possess the desired set ofproperties. Similarly, a molecular weight above about 10,000 indicatesformation of a product which does not possess the desired set ofdispersing properties or appropriate compatibility. As above discussed,the molecular weight of the polymer is determined by gel permeationchromatography using a polystyrene standard. Determination of molecularweights of polymers in this manner is well known.

The mixture of monomers used to make the above-described dispersant canadditionally consist essentially of a monomer selected from the groupconsisting of alkyl esters of acrylic acid wherein the alkyl groupcontains from 3 to 20 carbon atoms, alkyl esters of methacrylic acidwherein the alkyl group contains from 9 to 20 carbon atoms and mixturesthereof. The level of this monomer ranges from about 1 percent to about30 percent, preferably from about 5 percent to about 20 percent of thereaction mixture. The inclusion of this monomer is to maintainflexibility or aid in compatibility when so desired.

Pigment Dispersion Compositions

The aforedescribed dispersants permit the prior preparation ofdispersions of pigments or pigment mixtures which are subsequently usedin coating compositions. Each of the dispersions can be employed for thedirect pigmentation of coating compositions. The pigment dispersions canbe prepared at any convenient time and stored for future use.

The pigment dispersions of this invention consist essentially of fromabout 1 percent to about 50 percent, preferably from about 3 percent toabout 30 percent of the aforedescribed dispersant, from about 10 percentto about 90 percent, preferably about 15 percent to about 80 percent ofa pigment and the balance a liquid carrier. Pigments useful hereininclude those conventionally used in the coatings industry. Examples ofsuitable pigments include the iron oxides, lead chromates,silicochromate, stronium chromate, lead carbonate, lead sulfate, bariumcarbonate, china clay, calcium carbonate, aluminum silica, zinc oxide,zinc sulfide, zirconium oxide, antimony oxide, titanium dioxide, chromegreen, chrome yellow, thio-indigo red, phthalo blue, phthalo green,cobalt blue, cadmium yellow, cadmium red, toluidene red, graphite,carbon black, metallic aluminum, and metallic zinc.

The solvents used in the pigment dispersions are conveniently thesolvents used in the reaction of the monomers to form the interpolymer.However, other solvents can be added, such as xylene or mineral spirits.

The pigment dispersions can contain other additives commonly used inpigment dispersions, for example, plasticizers, wetting agents,defoamers, diluents and flow control agents.

Pigment dispersions are made by grinding or dispersing the pigment intothe dispersant. The grinding is usually accomplished by the use of ballmills, sand mills, Cowles dissolvers, continuous attritors and the like,until the pigment has been reduced to the desired size. After grinding,the particle size of the pigment is in the range of about 10 microns orless.

Coating Composition

The pigment dispersions described above are added to coatingcompositions either by the manufacturer and/or just prior to use by theconsumer as a tinting composition. The pigment dispersions arecompatible with a wide variety of film-forming resins and do notadversely affect the properties of a dried film made from the coatingcompositions. In particular, films made from the compositions of thisinvention have good color development and intercoat adhesion, i.e., havethe ability to adhere to a previously formed film. This latter featureis difficult to attain and represents an especially important featurepossessed by the compositions herein.

Useful coating compositions consist essentially of from about 25 percentto about 98 percent, preferably about 30 percent to about 80 percent ofthe film-forming resin, from about 1 percent to about 70 percent,preferably about 20 percent to about 60 percent of the pigment, fromabout 1 percent to about 50 percent, preferably about 2 percent to about30 percent of the dispersant and the balance liquid carrier. Suitablefilm-forming resins used in conjunction with the pigment dispersions aredescribed in the succeeding paragraphs. The film-forming resin can be anepoxy, vinyl, alkyd, polyester, acrylic, aminoplast, phenolplast,cellulose derivative, amide or urethane resin or mixtures thereof.Copolymers derived from such resins are also useful herein.

The epoxide resins used as a film-forming resin in the coatingcompositions are those compounds having a 1,2-epoxy group, i.e.,##STR2## present in the molecule. Polyepoxides contain more than one,1,2-epoxy group per molecule. In general, the epoxide equivalent weightwill range from about 140 to about 4,000. These polyepoxides aresaturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic,aromatic or heterocyclic. They can contain substituents such as halogen,hydroxyl and ether groups.

One useful class of polyepoxides comprises the epoxy polyethers obtainedby reacting an epihalohydrin (such as epichlorohydrin or epibromohydrin)with a polyphenol in the presence of an alkali. Suitable polyphenolsinclude resorcinol, catechol, hydroquinone,bis(4-hydroxyphenyl)-2,2-propane, i.e., bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenyl)-1,1-ethane; bis(2-hydroxynaphenyl)-methane; and1,5-hydroxynaphthalene. One very common polyepoxide is a polyglycidylether of a polyphenol, such as bisphenol A.

Another class of epoxy resins are the polyglycidyl ethers of polyhydricalcohols. These compounds may be derived from such polyhydric alcoholsas ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propyleneglycol, 1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol,glycerol, trimethylolpropane, and bis(4-hydroxycyclohexyl)-2,2-propane.

Another class of epoxide resins are the polyglycidyl esters ofpolycarboxylic acids. These compounds are produced by the reaction ofepichlorohydrin or a similar epoxy compound with an aliphatic oraromatic polycarboxylic acid such as oxalic acid, succinic acid,glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid anddimerized linoleic acid.

Still another class of polyepoxides are derived from the epoxidation ofan olefinically unsaturated alicyclic compound. These polyepoxides arenon-phenolic and are obtained by epoxidation of alicyclic olefins, forexample, by oxygen and selected metal catalysts, by perbenzoic acid, byacid-aldehyde monoperacetate or by peracetic acid. Among suchpolyepoxides are the epoxy alicyclic ethers and esters well known in theart.

Useful polyepoxides also include those containing oxyalkylene groups inthe epoxy molecule. Such oxyalkylene groups have the general formula:##STR3## where R is hydrogen or alkyl, preferably a lower alkyl havingfrom 1 to 6 carbon atoms, m is 1 to 4 and n is 2 to 50. Such groups arependant to the main molecular chain of the polyepoxide or are part ofthe main chain itself. The proportion of oxyalkylene groups in thepolyepoxide depends upon many factors, including the chain length of theoxyalkylene group, the nature of the epoxy and the degree of watersolubility desired.

Another class of polyepoxides consists of the epoxy novolac resins.These resins are obtained by reacting an epihalohydrin with thecondensation product of aldehyde and monohydric or polyhydric phenols. Atypical example is the reaction product of epichlorohydrin with aphenolformaldehyde condensate.

Any well-known curing reactant for the above-described epoxy resins isnormally included in the coating composition. It is well known chemicalsand resins containing functional groups with active hydrogen groups areuseful as curing agents for the epoxy resins. Generally, the curingagents cause polymerization by cross-linking of the epoxy molecules.Amine and polyamide catlysts are especially preferred curing agents.

Vinyl resins used in the coating compositions are derived from monomerscontaining a carbon to carbon double bond. These monomers polymerize bylinear addition to form long chain molecules. Generally, the polymericresins have the structure: ##STR4## wher R and R₁ represent variouspendant groups such as hydrogen, chlorine, acetate, benzene and toluene.The vinyl resins are commonly derived from the monomers vinyl chloride,vinylidene chloride, vinyl acetate, the vinyl acetals, styrene,acrylonitrile and mixtures thereof. The vinyl polymers and copolymersrange from about 100 to 10,000 carbon atoms in chain length and can beformed by bulk, solvent, suspension or emulsion polymerization.

Copolymers derived from mixtures of any of the aforedescribed vinylmonomers either with themselves or with other commonly usedpolymerizable monomers are used herein. Such copolymers possess a widerange of properties and can be formulated to fit individual needs.

One class of resins especially useful herein are the alkyd resins. Suchresins are polyesters of polyhydroxyl alcohols and polycarboxyl acidschemically combined with various drying, semi-drying and non-drying oilsin different proportions. Thus, for example, the alkyd resins are madefrom polycarboxylic acids such as phthalic acid, maleic acid, fumaricacid, isophthalic acid, succinic acid, adipic acid, azelaic acid,sebacic acid as well as from anhydrides of such acids, where they exist.The polyhydric alcohols which are reacted with the polycarboxylic acidinclude glycerol, trimethylolethane, trimethylolpropane,pentaerythritol, sorbitol, mannitol, ethylene glycol, diethylene glycoland 2,3-butylene glycol.

The alkyd resins are produced by reacting the polycarboxylic acid andthe polyhydric alcohol together with a drying, semi-drying or non-dryingoil in proportions depending upon the properties desired. The oils arecoupled into the resin molecule by esterification during themanufacturing and become an integral part of the polymer. The oil isfully saturated or predominately unsaturated. The fully saturated oilstend to give a plasticizing effect to the alkyd, whereas thepredominately unsaturated oils tend to cross-link and dry rapidly withoxidation to give more tough and durable alkyd resins. Suitable oilsinclude coconut oil, fish oil, linseed oil, tung oil, castor oil,cottonseed oil, safflower oil, soybean oil, and tall oil. Variousproportions of the polycarboxylic acid, polyhydric alcohol and oil areused to obtain alkyd resins of various properties.

Also useful herein are polyester type resins. As conventionally used andas used herein, the term "polyester" is applied to resins which containno oil or fatty acid modification. That is, while the above-describedalkyd resins are in the broadest sense polyester type resins, they areoil-modified and thus not generally considered a polyester resin. Thepolyesters are of two kinds. The more common are the unsaturatedpolyesters derived from unsaturated polyfunctional acids and polyhydricalcohol. These polyesters are essentially linear in structure. Maleicacid and fumaric acid are the usual unsaturated acid components.Commonly used polyhydric alcohols are ethylene glycol, propylene glycol,diethylene glycol, dipropylene glycol, butylene glycol, glycerol,trimethylol propane, pentaerythritol and sorbitol. Oftentimes asaturated acid will be included in the reaction to provide desirableproperties. Examples of saturated acids include phthalic acid,isophthalic acid, adipic acid, azelaic acid, sebacic acid and theanhydrides thereof where they exist. The saturated polyesters arederived from saturated or aromatic polyfunctional acids, preferablydicarboxylic acids, and mixtures of polyhydric alcohols having anaverage hydroxyl functionality greater than 2.

Useful acrylic resins are the polymerized ester derivatives of acrylicacid and methacrylic acid. The resins contain the units ##STR5##respectively. The esters are formed by the reaction of acrylic ormethacrylic acid with suitable alcohols, e.g., methyl alcohol, ethylalcohol, propyl alcohol, butyl alcohol and 2-ethylhexyl alcohol.Generally speaking, the larger the alcohol portion of the ester, thesofter and more flexible the resultant resin. Also, generally speaking,the methacrylate esters form harder films than the corresponding acrylicesters. Monomers such as styrene, vinyl toluene, vinyl chloride andvinylidine chloride may be reacted with the acrylic and methacrylicesters so as to produce resins with excellent properties.

Thermosetting acrylic resins are normally low molecular weightcopolymers made from 2 and sometimes 3 monomers. One of the monomers isan acrylic compound containing pendant reactive groups such as carboxyl,hydroxyl or amide. Another is an acrylic ester. The third monomer isusually a styrene type monomer such as styrene itself, vinyl toluene,methyl styrene or ethyl styrene. The proportions of the three componentsin the polymerization procedure are varied depending on the products inwhich the copolymer will be used.

Another class of film-forming resins useful in the coating compositionsherein is the amino resins commonly referred to as aminoplasts. Theamino resins are made by the reaction of an amine with an aldehyde. Themore important and preferred amines are urea and melamine. The aldehydecomponent comprises from 1 to 4 carbon atoms, with formaldehyde beingthe preferred aldehyde. Films of varying properties can be obtained bychanging the proportions of the amine and aldehyde and by adding variouschemically-reactive materials during the resin formation. Oftentimes, alower alcohol, especially butanol, is added during the resin formationto impart desirable properties to the amino resin.

The phenolic resins commonly referred to as phenoplasts are alsouseful-formers in the context of the subject invention. The phenolicresins are obtained by the condensation of phenol or substituted phenolswith aldehydes. The monohydric phenols such as phenol, cresol andxylanol are the most important since they are readily available andrelatively inexpensive. Phenol is the most preferred monohydric phenol.Polyhydric phenols such as resorcinol can also be used herein.Formaldehyde is the preferred aldehyde used in the production of thephenolic resins. Other aldehydes which are also useful includeacetaldehyde, butyraldehyde and furfuraldehyde. The preferred phenolicresin is produced by the condensation of phenol and formaldehyde.

Different cellulose derivatives useful herein include nitrocellulose,cellulose acetate, cellulose acetate butyrate and ethyl cellulose. Thesefilm-forming materials are well known and are commercially available invarying degrees of substitution and molecular weight. Nitrocellulose isthe preferred cellulose derivative.

Amide resins found to be useful include those polymers made bycondensing a diamine with a dibasic acid. They are characterized byrecurring amide groups, --CONH--, as an integral part of the mainpolymer chain. Examples of diamines used in producing the polyamideresins include ethylenediamine, diethylenetriamine andhexamethylenediamine. The carboxylic acids are the preferred dibasicacids and include adipic acid, sebacic acid, succinic acid, glutaricacid and azelaic acid.

Another class of film-formers used in the invention herein are theurethane resins. These are synthetic polymers that may be eitherthermoplastic or thermosetting. The basic polymeric unit is RNHCOOR. TheR groups can be the same or different and can contain other reactivegroups, for example, a second --NCO group, a second --OH group, etc.Typically, a polyhydric alcohol is reacted with a polyisocyanate toproduce the urethane resin. Useful polyhydric alcohols include ethyleneglycol, propylene glycol, butylene glycol, glycerol, trimethylolpropaneand hexane triol. Many variations are possible.

The urethane coating can be made from a one-pack of two-pack system. Theone-pack urethane contains either an isocyanate prepolymer or a blockedisocyanate. The prepolymers are prepared by the reaction of excessdiisocyanate with a polyhydric alcohol. Blocked isocyanates contain nofree isocyanate groups and are relatively inactive at room temperature.At elevated temperatures, the compounds diisociate and undergo reactionstypical of isocyanates. Typical blocking agents are phenols, thiols,tertiary alcohols and secondary aromatic amines. In a two-pack coatingsystem, typically a polyester polyol and an isocyanate (or isocyanateprepolymer for safety reasons) are mixed at the time of application andapplied immediately.

It will be recognized that a great many copolymers based upon theabove-described monomers are possible. Such copolymers possess a widerange of properties and can be formulated to fit individual needs. Thecopolymers are contemplated herein as being useful film-forming resinscompatible with the resin dispersants of this invention.

The balance of the compositions comprises a liquid carrier material.Many different organic solvents are suitable, examples of which includehydrocarbons and halogenated hydrocarbons such as toluene, xylene,mineral spirits, n-hexane, cyclohexane, chlorobenzene, andperchloroethylene.

Additives commonly used in coating compositions can be used herein also.Such additives include plasticizers, fillers, surfactants andstabilizers.

The coating compositions are applied by conventional coating techniquesonto a variety of substrates. Thus, the compositions can be applied byspraying, brushing, dipping, flow coating and roll coating. Substratesthat can be coated include wood, metals, glass, plastics and wallboard.

The examples which follow are illustrative of the invention. Allmolecular weights given are determined by gel permeation chromatographyusing a polystyrene standard.

EXAMPLE I

    ______________________________________                                        Isobutyl methacrylate  1117    grams                                          Methyl methacrylate    466.5   grams                                          Acrylic acid           42.1    grams                                          Dimethyloctadecylamine 37.2    grams                                          Hydroxyethyl acrylate  42.1    grams                                          2-Mercaptoethanol      25      grams                                          Tertiary butyl perbenzoate (TBPB)                                                                    116.8   grams                                          Ethylene glycol monobutyl ether                                                                      1525.7  grams                                          Denatured ethyl alcohol                                                                              30      grams                                          ______________________________________                                    

A reaction vessel is set up equipped with heating means, stirring means,means for maintaining a nitrogen blanket throughout the reaction andrefluxing means. A solvent blend of 1346 grams ethylene glycol monobutylether and the denatured alcohol is heated to reflux under a nitrogenblanket. At the reflux temperature a stream of the isobutylmethacrylate, methyl methacrylate, hydroxyethyl acrylate, acrylic acidand 2-mercaptoethanol and another stream of 83.4 grams of TBPB and 118grams of ethylene glycol monobutyl ether are added to the reactionmixture over a period of two hours. This mixture is held at reflux forone hour after the separate streams have been charged to the reactionvessel. Thereafter, the reaction is cooled to 120° C. at which time 33.4grams of TBPB and 61.7 grams of ethylene glycol monobutyl ether areadded over a period of one hour. This mixture is then held one hour at120° C. The resultant reaction mixture contains 50 percent solids andhas a Gardner-Holdt viscosity of H-I. The amine functional salt of theresin dispersant is formed by adding the dimethyloctadecyl amine to thereaction mixture.

The dispersant has a weight average molecular weight of 2200.

EXAMPLE II

The following components are utilized in forming a resin dispersant:

    ______________________________________                                        Isobutyl methacrylate  1278.9  grams                                          Methyl methacrylate    302.9   grams                                          Methacrylic acid       42.1    grams                                          Hydroxyethyl acrylate  42.1    grams                                          Dimethylaminoethyl methacrylate                                                                      16.8    grams                                          2-Mercaptoethanol      50.5    grams                                          Ethylene glycol monobutyl ether                                                                      1573.3  grams                                          Denatured ethyl alcohol                                                                              33.7    grams                                          Tertiary butyl perbenzoate (TBPB)                                                                    84.1    grams                                          ______________________________________                                    

A reaction vessel is set up equipped with heating means, stirring means,means for maintaining a nitrogen blanket throughout the reaction andrefluxing means. A solvent blend of 1346.1 grams of the ethylene glycolmonobutyl ether and the denatured ethyl alcohol is heated to refluxunder a nitrogen blanket. At the reflux temperature a stream of themethacrylic acid, hydroxyethyl acrylate, isobutyl methacrylate, methylmethacrylate, dimethylaminoethyl methacrylate, 2-mercaptoethanol and50.5 grams of ethylene glycol monobutyl ether and another separatestream of 75.7 grams of the TBPB and 75.7 grams of the ethylene glycolmonobutyl ether are added to the reaction mixture over a period of twohours. This mixture is held at reflux for one hour after the separatestreams have been charged to the reaction vessel. Thereafter, thereaction is cooled to 120° C. at which time 8.4 grams of TBPB and 176.7grams of ethylene glycol monobutyl ether are added over a period of onehour. This mixture is then held for one hour at 120° C.

The resultant mixture has a solids content of 49.6 percent and aGardner-Holdt viscosity of E-F. The dispersant has a molecular weight of1100.

EXAMPLE III

A reaction vessel is equipped as in Example I. The following componentsare used in the reaction:

    ______________________________________                                        Isobutyl methacrylate  1100.0  grams                                          Methyl methacrylate    466.5   grams                                          Acrylic acid           42.1    grams                                          Hydroxyethyl acrylate  42.1    grams                                          Dimethylaminoethyl methacrylate                                                                      16.7    grams                                          2-Mercaptoethanol      16.7    grams                                          Propasol B             1521.1  grams                                          Denatured ethyl alcohol                                                                              30.0    grams                                          Ethyl alcohol          72.9    grams                                          Tertiary butyl perbenzoate (TBPB)                                                                    84.1    grams                                          ______________________________________                                    

Propasol B is an isomeric mixture of n-butoxy propanol available fromthe Union Carbide Corp.

The reaction vessel is initially charged with 1346.1 grams of Propasol Band the denaturated ethyl alcohol. This solvent mixture is heated toreflux, i.e., about 145° C. Thereafter over the next two hours, separatestreams of (1) the acrylic acid, hydroxyethyl acrylate, isobutylmethacrylate, methyl methacrylate, dimethylaminoethyl methacrylate,2-mercaptoethanol and 50.5 grams of the Propasol B and (2) 75.7 grams ofthe TBPB and 75.7 grams Propasol B are added. The temperature isadjusted to 120° C. with the ethyl alcohol. Over the next one hour, 8.4grams of TBPB and 103.8 grams of Propasol B are added. This mixture isthen held for one hour and cooled.

The reaction mixture is comprised of 49.5 percent solids and has aGardner-Holdt viscosity of K-L. The dispersant has a molecular weight of2200.

EXAMPLE IV

The following components are used to produce a resin dispersant:

    ______________________________________                                        Isobutyl methacrylate  1278.9  grams                                          Methyl methacrylate    302.9   grams                                          Methacrylic acid       58.9    grams                                          Hydroxyethyl acrylate  42.1    grams                                          2-Mercaptoethanol      50.5    grams                                          Ethylene glycol monobutyl ether                                                                      1648.0  grams                                          Tertiary butyl perbenzoate (TBPB)                                                                    84.1    grams                                          Propylenimine          10.8    grams                                          Denatured ethyl alcohol                                                                              33.7    grams                                          ______________________________________                                    

A reaction vessel is set up as in Example I. Initially, 1346.1 grams ofethylene glycol monobutyl ether and 33.7 grams of the denatured ethylalcohol are charged to the reaction vessel and heated to 144° C.Thereafter separate streams of (1) the methacrylic acid, hydroxyethylacrylate, methyl methacrylate, 2-mercaptoethanol and 50.5 grams of theethylene glycol monobutyl ether and of (2) 75.7 grams of TBPB and 75.7grams of the ethylene glycol monobutyl ether are added to the reactionvessel. The temperature during this addition is maintained at 140° C.with the addition made over a period of about 2 hours. The mixture iscooled to 120° C. with ethanol and 177 grams of ethylene glycolmonobutyl ether and 8.4 grams of TBPB are added over one hour. Thereaction is cooled to 55° C. and when this temperature is reached, thepropylenimine is added and the reaction mixture held at 65°-70° C. for atime period of two hours.

The reaction mixture is analyzed and found to contain 50.9 percentsolids. It has a Gardner-Holdt viscosity of G-H. The dispersant's weightaverage molecular weight is 2600.

EXAMPLE V

A resin dispersant is made following the procedure of Example IV exceptacrylic acid is used in place of the methacrylic acid, 1100.0 grams ofthe isobutyl methacrylate is used instead of the 1278.9 grams and 471.2grams of the methyl methacrylate is used instead of the 302.9 grams. Thefinal reaction mixture contains 50 percent solids. The dispersant'sweight average molecular weight is 3000.

EXAMPLE VI

A resin dispersant is made following the procedure of Example III except933.7 grams of 2-ethylhexyl methacrylate is used in place of theisobutyl methacrylate and 633.6 grams, instead of 466.5 grams, of methylmethacrylate is used. The dispersant's weight average molecular weightis 4600.

EXAMPLE VII

Example III is repeated except butyl methacrylate is used in place ofthe isobutyl methacrylate, at the same level. The resultant solutioncontaining the resin dispersant has a solids content of 49.6 percent.The weight average molecular weight of the dispersant is 5600.

EXAMPLE VIII

Another resin dispersant is made following the procedure of Example IVexcept 1083.8 grams butyl methacrylate is used in place of the isobutylmethacrylate, 466.5 grams methyl methacrylates is used and 55.8 grams ofacrylic acid is used in place of the methacrylic acid. The dispersant'sweight average molecular weight is 5800.

EXAMPLE IX

A resin dispersant using butyl methacrylate and styrene in place ofisobutyl methacrylate and methyl methacrylate, respectively, and atequal levels is made using the procedure described in Example III. Theresultant dispersant's weight average molecular weight is 5600.

EXAMPLE X

The dispersant of Example III is used to formulate pigment dispersionshaving the following compositions:

    ______________________________________                                                           Dispersant                                                         Pigment Percent                                                                          Percent   Solvent Percent                                  ______________________________________                                        Black tint (1)                                                                          20           16        64                                           White tint (2)                                                                          74           5.2       20.8                                         Yellow tint (3)                                                                         55           9         36                                           Red tint (4)                                                                            68           6.4       25.6                                         Blue tint (5)                                                                           20           16        64                                           Green tint (6)                                                                          18           16.4      65.6                                         ______________________________________                                         (1) The pigment is a #6 Lamp Black available from General Carbon Co.          (2) The pigment is Titantium Dioxide R 960 available from E. I. Dupont De     Nemours & Co., Inc.                                                           (3) The pigment is Yellow Iron Oxide 1888D available from Pfizer Inc.         (4) The pigment is Red Iron Oxide R3098 available from Pfizer Inc.            (5) The pigment is Phthalo Blue BT 425D available from E. I. Dupont De        Nemours & Co., Inc.                                                           (6) The pigment is Phthalo Green GT 751D available from E. I. Dupont De       Nemours & Co., Inc.                                                      

The solvent is an isomeric mixture of n-butoxy propanol available fromUnion Carbide Corp. as Propasol B.

The pigment dispersions are made by first premixing the pigment,dispersant and solvent on a Cowles mixer for about 20 minutes to form awell wetted uniform mix. Next, the premix is ground on a Sussmeyer milluntil the resultant paste possesses a Hegmann Grind Gauge reading of +7.Optionally, a portion of the dispersant and solvent is held back fromthe initial premixing step and is used to wash down the Sussmeyer mill.The wash is added to the previously milled paste to form pastes havingthe above compositions.

EXAMPLE XI

The pigment dispersion of this invention is tested for tintcompatibility with paints containing different film-forming resins asdescribed below. The pigment dispersion used in this example is theblack tint pigment dispersion of Example X.

    ______________________________________                                                                          Percent                                                                       Volatile                                                   Percent  Percent   Curriers,                                   Film-Forming   Film-    Pigment   Flow Control                                Resin Type     Former   Dispersion                                                                              Agents, etc.                                ______________________________________                                        (A)  80 percent tall oil                                                                         37.2     6.2     Balance                                        fatty acid alkyd                                                              resin cross-linked                                                            with 20 percent                                                               aminoplast (1)                                                           (B)  Acrylic resin (2)                                                                           32.5     5.4     "                                         (C)  Vinyl toluene alkyd                                                                         24.8     4.1     "                                              copolymer (3)                                                            (D)  Acrylic/epoxy co-                                                                           20.7     3.5     "                                              polymer (4).                                                             (E)  Plasticized acrylic                                                                         22.4     3.7     "                                              lacquer (5)                                                              (F)  Vinyl resin (6)                                                                             28.2     4.7     "                                         (G)  Medium oil alkyd                                                                            30.4     5.1     "                                              resin (7)                                                                (H)  Acrylic/melamine                                                                            29.7     4.9     "                                              copolymer (8)                                                            (I)  Nitrocellulose/                                                                             16.7     2.8     "                                              alkyd lacquer (9)                                                        ______________________________________                                         (1) The aminoplast is available from Monsanto Co. as Resimine 735.            (2) The acrylic resin is an internally crosslinked acrylic resin found in     PPG Industries, Inc. DURACRON 200.                                            (3) A vinyl toluated alkyd resin.                                             (4) A 90:10 blend of an internally crosslinked acrylic resin of Example       (B) and EPON 1001, available from Shell Chemical Co.                          (5) An air dry lacquer acrylic resin having imine modification made by PP     Industries, Inc.                                                              (6) A resin blend of 78 percent of a solution vinyl resin and 22 percent      of a chlorinated paraffin.                                                    (7) Derived from 59 percent soya oil, 29 percent phthalic anhydride and 1     percent pentaerythritol.                                                      (8) A hydroxy functional acrylic resin crosslinked with an aminoplast.        (9) A 35/65 blend of a nitrocellulose solution and tall oil fatty acid        glycerol alkyd resin.                                                    

Compatibility of the pigment dispersions with the film-forming resins inthe respective paints and their effect on the properties of a formedfilm are determined using a series of tests. Initially, the paints areshaken for 10 to 15 minutes and allowed to digest overnight. Then 1.0 to1.2 mil (dry) films of the paints on steel panels are formed byspraying.

Compatibility is determined by a rub-up test. While the films on theabove-described steel panels are still wet, they are rubbed with theforefinger. Any lightening of the color is noted. A noticeable change incolor between the rubber portion of the wet film and the unrubbedportion is an indication of incompatibility of the pigment dispersionsin the paint. The following rub-up values are obtained based on a 0 to10 scale with 0 being no change in color and 5 being the value abovewhich a significant color change and hence a compatibility problem isexperienced.

    ______________________________________                                        Paint            Rub-up                                                       ______________________________________                                        (A)              3                                                            (B)              1                                                            (C)              1                                                            (D)              3                                                            (E)              2                                                            (F)              2                                                            (G)              2                                                            (H)              1                                                            (I)              1                                                            ______________________________________                                    

The above results show that the pigment dispersion of this invention iscompatible with a wide variety of film-forming resins.

The effect the pigment dispersions have on the properties of the formedfilms is determined using a (1) direct and reverse impact test, (2)pencil hardness test, and (3) intercoat adhesion test. The impact testsare conducted using a Gardner Variable Impact Tester. The pencilhardness test is a measure of the film's hardness. A hardness value isassigned a film based on its ability to withstand pressure applied by apencil having a specified grade of lead. The intercoat adhesion testmeasures the ability of the formed film to adhere to a previously coatedsubstrate.

In all instances, coating compositions (A)-(I) have substantiallyequivalent or better properties than controls where the above describedpigment dispersions are omitted.

EXAMPLE XII

Resin dispersants made from the compounds indicated in the chart(expressed as percents) are tested for compatibility and their effect onfilm properties of a paint containing them. Resin dispersants A, B, C,D, E, F and G correspond with the dispersants of Examples III, V, I, VI,VII, VIII and IX, respectively.

    ______________________________________                                        Resin dispersant  A     B     C   D   E   F    G                              ______________________________________                                        Isobutyl methacrylate                                                                           66    66    66  --  --  --   --                             2-Ethylhexyl methacrylate                                                                       --    --    --  56  --  --   --                             Butyl methacrylate                                                                              --    --    --  --  66  65.5 66                             Methyl methacrylate                                                                             28    28    27  38  28  28   --                             Styrene           --    --    --  --  --  --   28                             Acrylic acid      2.5   2.5   2.5 2.5 2.5 2.5  2.5                            Hydroxyethyl acrylate                                                                           2.5   2.5   2.5 2.5 2.5 2.5  2.5                            Amino functional moiety (1)                                                                      1    --    --   1   1  --    1                             Amino functional moiety (2)                                                                     --     1    --  --  --  1.5  --                             Amino functional moiety (3)                                                                     --    --     2  --  --  --   --                             ______________________________________                                         (1) The amino functional moiety is provided by polymerizing                   dimethylaminoethyl methacrylate into the resin dispersant's polymeric         backbone.                                                                     (2) The amino functional moiety is provided by an aziridine ring opening      reaction.                                                                     (3) An amine salt of the resin dispersant is formed from the dispersant       and dimethyloctodecyl amine.                                             

The above resin dispersants are tested by adding them at a 6 percentlevel to (1) an internally cross-linked acrylic resin based paint and(2) an alkyd/melamine based paint. Values for color development, rub-upand intercoat adhesion are obtained. The color development value is ameasure of the resin dispersant's efficiency as determined by itsability to evenly disperse pigment throughout the dried film. A value of1 is excellent, 10 poor and 5 marginally acceptable.

    ______________________________________                                        Cross-Linked Acrylic Resin Based Paint                                        Resin Dispersant                                                                         Color Development                                                                           Rub-Up    Adhesion                                   ______________________________________                                        A          4             3         o.k.                                       B          4             2         o.k.                                       C          3             2         o.k.                                       D          2             1         o.k.                                       E          2             2         o.k.                                       F          2             3         o.k.                                       G          2             1         o.k                                        ______________________________________                                        Alkyd/Melamine Resin Based Paint                                              Resin Dispersant                                                                         Color Development                                                                           Rub-Up    Adhesion                                   ______________________________________                                        A          1             3         o.k.                                       B          3             3         o.k.                                       C          2             3         o.k.                                       D          2             3         o.k.                                       E          2             3         o.k.                                       F          2             3         o.k.                                       G          2             3         o.k.                                       ______________________________________                                    

The above results show the resin dispersants of this invention performsatisfactorily as pigment dispersants, are compatible with the testedcoating composition and do not have an adverse effect on the formedfilm's intercoat adhesion.

What is claimed is:
 1. A dispersant compatible with a variety ofresin-containing coating compositions and especially adapted fordispersing pigments therein, said dispersant being the polymerizationproduct of a mixture of monomers consisting essentially of:(i) fromabout 20 percent to about 85 percent of an alkyl methacrylate havingfrom 3 to 8 carbon atoms in the alkyl group; (ii) from about 5 percentto about 60 percent of a hardening monomer selected from the groupconsisting of a styrene, methyl methacrylate, ethyl methacrylate andmixtures thereof; and (iii) from about 2 percent to about 50 percent ofan ethylenically unsaturated carboxylic acid selected from the groupconsisting of acrylic acid, methacrylic acid, itaconic acid, crotonicacid, maleic acid, fumaric acid and mixtures thereof with at least about1 percent to about 25 percent of the carboxylic acid being acrylic acidor methacrylic acid; and (iv), wherein (iv) is a compound which providesan amine or amine salt functional moiety on the polymerization productat a level of from about 0.1 percent to about 15 percent is provided by(1) a nitrogen-containing ring opening compound having the formula##STR6## where R₁, R₂, R₄, R₅, and R₆ are each selected from the groupconsisting of hydrogen, alkyl, aryl, alkaryl and aralkyl, R₃ is selectedfrom the group consisting of hydrogen and lower alkyl and n is 0 or 1,which can be either reacted with the polymerization product of monomers(i) through (iii) or polymerized with monomers (i) through (iii), (2) anacrylic or methacrylic compound containing amino groups which ispolymerized with monomers (i) through (iii) or (3) an aliphatic oralicyclic amine compound which forms a salt with carboxyl moieties ofthe polymerization product of monomers (i) through (iii), furtherwherein the polymerization product of monomers (i) through (iii) and(iv) is reacted with an epoxide to provide hydroxyl groups, the amountof epoxide being adjusted so that from about 1 percent to about 25percent of units provided by monomer (iii) are reacted with the epoxideand from about 1 percent to about 25 percent of units provided bymonomer (iii) are not reacted with the epoxide and further wherein saiddispersant has a weight average molecular weight, determined by gelpermeation chromotography, using a polystyrene standard, of from about1,000 to about 10,000.
 2. A dispersant compatible with a variety ofresin-containing coating compositions and especially adapted fordispersing pigments therein, said dispersant being the polymerizationproduct of a mixture of monomers consisting essentially of:(i) fromabout 20 percent to about 85 percent of an alkyl methacrylate havingfrom 3 to 8 carbon atoms in the alkyl group; (ii) from about 5 percentto about 60 percent of a hardening monomer selected from the groupconsisting of a styrene, methyl methacrylate, ethyl methacrylate andmixtures thereof: (iii) from about 1 percent to about 25 percent of amonomer having a double bond alpha-beta to a carbonyl group, saidmonomer being an alkyl acrylate; and (iv) from about 1 percent to about25 percent of an acrylic or methacrylic acid; wherein the polymerizationproduct of monomers (i) through (iv) is further reacted with water toprovide carboxyl functionality from units provided by the alkyl acrylatemonomer and is further reacted with epoxide to provide hydroxyl groupsfrom units provided by the acrylic or methacrylic acid, with theexception of (v) (3), and (v), wherein (v) is a compound which providesan amine or amine salt functional moiety on the polymerization productat a level of from about 0.1 percent to about 15 percent is provided by(1) a nitrogen-containing ring opening compound having the formula##STR7## where R₁, R₂, R₄, R₅, and R₆ are each selected from the groupconsisting of hydrogen, alkyl, aryl, alkaryl and aralkyl, R₃ is selectedfrom the group consisting of hydrogen and lower alkyl and n is 0 or 1,which is reacted with the polymerization product of monomers (i) through(iv) after said product has been reacted with the water and the epoxide,(2) an aliphatic or alcyclic amine compound which forms a salt with thecarboxyl moieties of the polymerization product of monomers (i) through(iv) after said product has been reacted with the water and the epoxide,or (3) an acrylic or methacrylic compound containing amino groups whichis polymerized with monomers (i) through (iv), further wherein thepolymerization product of monomers (i) through (iv) and (v) (3) isreacted with water to provide carboxyl functionality from units providedby (iii) and is further reacted with epoxide to provide hydroxyl groupsfrom units provided by (iv) and further wherein said dispersant has aweight average molecular weight, determined by gel permeationchromotography, using a polystyrene standard, of from about 1,000 toabout 10,000.
 3. A dispersant compatible with a variety ofresin-containing coating compositions and especially adapted fordispersing pigments therein, said dispersant being the polymerizationproduct of a mixture of monomers consisting essentially of:(i) fromabout 20 percent to about 85 percent of an alkyl methacrylate havingfrom 3 to 8 carbon atoms in the alkyl group; (ii) from about 5 percentto about 60 percent of a hardening monomer selected from the groupconsisting of a styrene, methyl methacrylate, ethyl methacrylate andmixtures thereof; (iii) from about 1 percent to about 25 percent of amonomer having a double bond alpha-beta to a carbonyl group, saidmonomer being an unsaturated carboxylic anhydride; and (iv) from about 1percent to about 25 percent of an acrylic or methacrylic acid;whereinthe polymerization product of monomers (i) through (iv) is furtherreacted with water, alcohol or amine to provide carboxyl functionalityfrom units provided by the unsaturated carboxylic anhydride monomer andis further reacted with epoxide to provide hydroxyl groups from unitsprovided by the acrylic or methacrylic acid, with the exception of (v)(3), and (v), wherein (v) is a compound which provides an amine or aminesalt functional moiety on the polymerization product at a level of fromabout 0.1 percent to about 15 percent is provided by (1) anitrogen-containing ring opening compound having the formula ##STR8##where R₁, R₂, R₄, R₅, and R₆ are each selected from the group consistingof hydrogen, alkyl, aryl, alkaryl and aralkyl, R₃ is selected from thegroup consisting of hydrogen and lower alkyl and n is 0 or 1, which isreacted with the polymerization product of monomers (i) through (iv)after said product has been reacted with the water, alcohol or amine andthe epoxide, (2) an aliphatic or alicyclic amine compound which forms asalt with the carboxyl moieties of the polymerization product ofmonomers (i) through (iv) after said product has been reacted with thewater, alcohol or amine and the epoxide, or (3) an acrylic ormethacrylic compound containing amino groups which is polymerized withmonomers (i) through (iv), further wherein the polymerization product ofmonomers (i) through (iv) and (v) (3) is reacted with water, alcohol oramine to provide carboxyl functionality from units provided by (iii) andis further reacted with epoxide to provide hydroxyl groups from unitsprovided by (iv) and further wherein said dispersant has a weightaverage molecular weight, determined by gel permeation chromotography,using a polystyrene standard, of from about 1,000 to about 10,000.
 4. Adispersant compatible with a variety of resin-containing coatingcompositions and especially adapted for dispersing pigments therein,said dispersant being the polymerization product of a mixture ofmonomers consisting essentially of:(i) from about 20 percent to about 85percent of an alkyl methacrylate having from 3 to 8 carbon atoms in thealkyl group; (ii) from about 5 percent to about 60 percent of ahardening monomer selected from the group consisting of a styrene,methyl methacrylate, ethyl methacrylate and mixtures thereof; (iii) fromabout 1 percent to about 25 percent of a monomer having a double bondalpha-beta to a carbonyl group, said monomer being a hydroxy-containingmonomer; and (iv) from about 1 percent to about 25 percent of an acrylicor methacrylic acid;wherein the polymerization product of monomers (i)through (iv) is further reacted with an anhydride to provide carboxylfunctionality from units provided by the hydroxy-containing monomer andis further reacted with epoxide to provide hydroxyl groups from unitsprovided by the acrylic or methacrylic acid, with the exception of (v)(3), and (v), wherein (v) is a compound which provides an amine or aminesalt functional moiety on the polymerization product at a level of fromabout 0.1 percent to about 15 percent is provided by (1) anitrogen-containing ring opening compound having the formula ##STR9##where R₁, R₂, R₄, R₅, and R₆ are each selected from the group consistingof hydrogen, alkyl, aryl, alkaryl and aralkyl, R₃ is selected from thegroup consisting of hydrogen and lower alkyl and n is 0 or 1, which isreacted with the polymerization product of monomers (i) through (iv)after said product has been reacted with the anhydride and the epoxide,(2) an aliphatic or alicyclic amine compound which forms a salt with thecarboxyl moieties of the polymerization product monomers (i) through(iv) after said product has been reacted with the anhydride and theepoxide, or (3) an acrylic or methacrylic compound containing aminogroups which is polymerized with monomers (i) through (iv), furtherwherein the polymerization product of monomers (i) through (iv) and (v)(3) is reacted with anhydride to provide carboxyl functionality fromunits provided by (iii) and is further reacted with epoxide to providehydroxyl groups from units provided by (iv) and further wherein saiddispersant has a weight average molecular weight, determined by gelpermeation chromotography, using a polystyrene standard, of from about1,000 to about 10,000.
 5. A dispersant compatible with a variety ofresin-containing coating compositions and especially adapted fordispersing pigments therein, said dispersant being the polymerizationproduct of a mixture of monomers consisting essentially of:(i) fromabout 20 percent to about 85 percent of an alkyl methacrylate havingfrom 3 to 8 carbon atoms in the alkyl group; (ii) from about 5 percentto about 60 percent of a hardening monomer selected from the groupconsisting of a styrene, methyl methacrylate, ethyl methacrylate andmixtures thereof; (iii) from about 1 percent to about 25 percent of amonomer having a double bond alpha-beta to a carbonyl group, saidmonomer being an amine-containing monomer; and (iv) from about 1 percentto about 25 percent of an acrylic or methacrylic acid;wherein thepolymerization product of monomers (i) through (iv) is further reactedwith an anhydride to provide carboxyl functionality from units providedby the amine-containing monomer (iii) and is further reacted withepoxide to provide hydroxyl groups from units provided by the acrylic ormethacrylic acid, with the exception of (v)(3), and (v), wherein (v) isa compound which provides an amine or amine salt functional moiety onthe polymerization product at a level of from about 0.1 percent to about15 percent is provided by (1) a nitrogen-containing ring openingcompound having the formula ##STR10## where R₁, R₂, R₄, R₅, and R₆ areeach selected from the group consisting of hydrogen, alkyl, aryl,alkaryl and aralkyl, R₃ is selected from the group consisting ofhydrogen and lower alkyl and n is 0 or 1, which is reacted with thepolymerization product of monomers (i) through (iv) after said producthas been reacted with the anhydride and the epoxide, (2) an aliphatic oralicyclic amine compound which forms a salt with the carboxyl moietiesof the polymerization product of monomers (i) through (iv) after saidproduct has been reacted with the anhydride and the epoxide, or (3) anacrylic or methacrylic compound containing amino groups which ispolymerized with monomers (i) through (iv) further wherein thepolymerization product of monomers (i) through (iv) and (v)(3) isreacted with anhydride to provide carboxyl functionality from unitsprovided by (iii) and is further reacted with epoxide to providehydroxyl groups from units provided by (iv) and further wherein saiddispersant has a weight average molecular weight, determined by gelpermeation chromotography, using a polystyrene standard, of from about1,000 to about 10,000.
 6. The dispersant of claims 1, 2, 3, 4 or 5 beingthe polymerization product of a mixture of monomers consistingessentially of:(i) from about 40 percent to about 80 percent of thealkyl methacrylate having from 3 to 8 carbon atoms in the alky group;(ii) from about 15 percent to about 40 percent of the hardening monomer;(iii) from about 1 percent to about 20 percent of the ethylenicallyunsaturated carboxylic acid or the monomer which provides the carboxylfunctionality when further reacted; (iv) from about 1 percent to about15 percent of the acrylic or methacrylic acid; and (v) from about 0.5percent to about 3 percent of the compound providing an amine or aminesalt functional moiety.
 7. The dispersant of claim 6 wherein monomer(iii) is the ethylenically unsaturated carboxylic acid.
 8. Thedispersant of claim 7 wherein the alkyl methacrylate is a branched chainmethacrylate.
 9. The dispersant of claim 8 wherein the alkylmethacrylate is isobutyl methacrylate.
 10. The dispersant of claim 8wherein the hardening monomer is styrene or methyl methacrylate.
 11. Thedispersant of claim 10 wherein the ethylenically unsaturated carboxylicacid is acrylic acid or methacrylic acid.
 12. The dispersant of claim 6wherein the component providing an amine or amine salt functional moietyis an aliphatic or alicyclic amine compound which forms a salt with thecarboxyl moiety of the interpolymer.
 13. The dispersant of claim 6wherein the component providing an amine or amine salt functional moietyis an acrylic or methacrylic compound containing amino groups.
 14. Thedispersant of claim 6 wherein the amine or amine salt functional moietyis provided by a nitrogen-containing ring opening compound.
 15. Thedispersant of claim 6 additionally consisting essentially of from about1 percent to about 30 percent of a monomer selected from the groupconsisting of alkyl esters of acrylic acid wherein the alkyl groupcontains from 3 to 20 carbon atoms, alkyl esters of methacrylic acidwherein the alkyl group contains from 9 to 20 carbon atoms and mixturesthereof.
 16. The dispersant of claim 6 being the polymerization productof a mixture of monomers consisting essentially of:(i) from about 60percent to about 80 percent of the alkyl methacrylate having from 3 to 8carbon atoms in the alkyl group; (ii) from about 20 percent to about 35percent of the hardening monomer; (iii) from about 1 percent to about 15percent of the ethylenically unsaturated carboxylic acid or the monomerwhich provides the carboxyl functionality when further reacted; (iv)from about 1 percent to about 10 percent of the acrylic or methacrylicacid; and (v) from about 0.5 percent to about 3 percent of the compoundproviding an amine or amine salt functional moiety.
 17. The dispersantof claim 16 wherein the dispersant has a weight average molecular weightof from about 2,000 to about 6,000.
 18. A pigment dispersion compositionadapted for dispersing pigments in a film-forming resin-containingcoating composition wherein said pigment dispersion composition consistsessentially of:(a) from about 1 percent to about 50 percent of thedispersant of claims 1, 2, 3, 4 or 5; (b) from about 10 percent to about90 percent of a pigment; and (c) the balance, a liquid carrier.
 19. Thecomposition of claim 18 wherein the dispersant is the polymerizationproduct of a mixture of monomers consisting essentially of:(i) fromabout 40 percent to about 80 percent of the alkyl methacrylate havingfrom 3 to 8 carbon atoms in the alkyl group; (ii) from about 15 percentto about 40 percent of the hardening monomer; (iii) from about 1 percentto about 20 percent of the ethylenically unsaturated carboxylic acid orthe monomer which provides the carboxyl functionality when furtherreacted; (iv) from about 1 percent to about 15 percent of the acrylic ormethacrylic acid; and (v) from about 0.5 percent to about 3 percent ofthe compound providing an amine or amine salt functional moiety.
 20. Thecomposition of claim 19 monomer (iii) is the ethylenically unsaturatedcarboxylic acid.
 21. The composition of claim 20 wherein the alkylmethacrylate is a branched chain methacrylate.
 22. The composition ofclaim 21 wherein the alkyl methacrylate is isobutyl methacrylate. 23.The composition of claim 21 wherein the hardening monomer is styrene ormethyl methacrylate.
 24. The composition of claim 23 wherein theethylenically unsaturated carboxylic acid is acrylic acid or methacrylicacid.
 25. The composition of claim 19 wherein the component providing anamine or amine salt functional moiety is an aliphatic or alicyclic aminecompound which forms a salt with the carboxyl moiety of theinterpolymer.
 26. The composition of claim 19 wherein the componentproviding an amine or amine salt functional moiety is an acrylic ormethacrylic compound containing amino groups.
 27. The composition ofclaim 19 wherein the amine or amine salt functional moiety is providedby a nitrogen-containing ring opening compound.
 28. The composition ofclaim 19 wherein the dispersant additionally consists essentially offrom about 1 percent to about 30 percent of a monomer selected from thegroup consisting of alkyl esters of acrylic acid wherein the alkyl groupcontains from 3 to 20 carbon atoms, alkyl esters of methacrylic acidwherein the alkyl group contains from 9 to 20 carbon atoms and mixturesthereof.
 29. The composition of claim 24 wherein the dispersant is thepolymerization product of:(i) from about 60 percent to about 80 percentof the alkyl methacrylate having from 3 to 8 carbon atoms in the alkylgroup; (ii) from about 20 percent to about 35 percent of the hardeningmonomer; (iii) from about 1 percent to about 15 percent of theethylenically unsaturated carboxylic acid or the monomer which providesthe carboxyl functionality when further reacted; (iv) from about 1percent to about 10 percent of the acrylic or methacrylic acid; and (v)from about 0.5 percent to about 3 percent of the compound providing anamine or amine salt functional moiety.
 30. The composition of claim 29wherein the dispersant has a molecular weight of from about 2,000 toabout 6,000.
 31. The composition of claim 19 consisting essentiallyof:(a) from about 3 percent to about 30 percent of the dispersant; (b)from about 15 percent to about 80 percent of the pigment; and (c) thebalance a liquid carrier.
 32. The composition of claim 31 wherein thecarrier is an organic solvent.
 33. The composition of claim 18 whereinthe pigment is ground into the dispersant.